Twin roll caster

ABSTRACT

A twin roll caster including chilled rolls, side weirs, and a molten-metal delivery nozzle. Baffles, contiguous with bottoms of end faces of the nozzle, project in a casting pool toward the side weirs to suppress stream of the molten metal into a nip between the rolls. Thus, hot molten metal just after poured into the pool does not instantly reach the nip along the side weirs, and molten metal decreases in temperature with lapse of time after the pouring streams into the nip as the rolls are rotated. As a result, belated formation of solidified shells at and adjacent to outer circumferential edges of the chilled rolls is eliminated. Thus, a strip delivered from the nip between the rolls has no reduced thickness at regions adjacent to lateral edges of the strip and has uniform thickness throughout the width of the strip.

TECHNICAL FIELD

The present invention relates to a twin roll caster.

BACKGROUND ART

Known as one of techniques for directly producing a strip from moltenmetal is twin-roll continuous casting where molten metal is supplied tobetween a pair of rotated rolls to deliver a solidified metal striptherefrom.

FIG. 1 shows a convention twin roll caster comprising a pair of chilledrolls 1 arranged horizontally side by side and a pair of side weirs 2associated with the rolls 1.

The chilled rolls 1 are constructed such that cooling water passesthrough the rolls and a nip G between the rolls may beexpanded/contracted depending on thickness of the strip 3 to beproduced.

The rotated speed and direction of the chilled rolls 1 are set such thatouter circumferential surfaces of the respective rolls move from aboveto the nip G between the rolls at the same speed.

One of the side weirs 2 surface-contact one ends of the respectivechilled rolls 1 and the other side weir 2, the other ends of the rolls1. In a space defined by the chilled rolls 1 and the side weirs 2, amolten-metal delivery nozzle 4 made from refractory material is arrangedjust above the nip G between the rolls.

The delivery nozzle 4 has a top with an elongated nozzle trough 6 forreceiving molten metal 5 and has longitudinal side walls formed withopenings 7 from the trough 6 toward the outer circumferential surfacesof the chilled rolls 1, the openings 7 being formed on the side wallsadjacent to lower ends thereof and being aligned along axes of the rolls1. When the molten metal is poured into the nozzle trough 6, a castingpool 8 is formed above the nip G between the rolls 1 and in contact withthe outer circumferential surfaces of the rolls 1.

Thus, with the casting pool 8 being formed, the rolls 1 are rotatedwhile being cooled by circulation of cooling water, so that the moltenmetal 5 is solidified on the outer circumferential surfaces of the rolls1 to deliver a strip 3 downwardly from the nip G.

In so-called triple point regions where the rolls 1, the side weirs 2and the casting pool 8 meet, the solidified shells may be producedabnormally.

If such solidified shells at the triple point regions were drawn andpeeled away by the solidified shells on the outer circumferentialsurfaces of the rolls 1, they might be drawn into the nip G between therolls 1, resulting in not only defective shape in the form of locallythickened strip 3, but also deteriorated cooling efficiency due to theflared nip G by the locally thickened strip, breakage of the strip 3 dueto thermal recuperation from the molten metal 5 and/or impair of theside weirs 2 upon drop of the solidified shells.

Thus, a twin roll caster has been proposed which directs molten metal 5to side weirs 2 and especially positively in a direction tangent tochilled rolls 1 so as to suppress formation of undesired solidifiedshell (see, for example, Patent Literature 1).

[Patent Literature 1] JP62-45456A

SUMMARY OF INVENTION Technical Problems

However, in the twin roll caster according to the Patent Literature 1,the hot molten metal 5 just after the pouring streams along the sideweirs 2 to reach the nip G within an extremely short time, so that thesolidified shells are produced belatedly at regions adjacent to edges ofthe outer circumferential surfaces of the chilled rolls 1.

As a result, the strip 3 delivered from the nip G tends to have reducedthickness at its lateral ends or edges, resulting in difficulty ofhaving uniform thickness throughout the width of the strip 3.

The invention was made in view of the above and has its object toprovide a twin roll caster which can suppress reduction in thickness ofa strip at lateral edges thereof.

Solution to Problems

In order to attain the above object, the invention is directed to a twinroll caster with chilled rolls, side weirs and a molten-metal deliverynozzle, comprising baffles capable of suppressing stream of molten metalalong the side weirs into a nip between the rolls.

More specifically, the baffles are projected from bottoms of end facesof the nozzle in a casting pool toward the side weirs, respectively;alternatively, the baffles are projected from the side weirs in thecasting pool toward the bottoms of the end faces of the nozzle,respectively.

Alternatively, ends of the nozzle extend to the side weirs,respectively, the baffles being projected from intermediate portions ona bottom of the nozzle toward said side weirs so as to form voidsbetween the baffles and the bottom of the nozzle, respectively.

According to the invention, in order that the hot molten metal justafter the pouring does not stream along the side weirs to instantlyreach the nip, the baffles suppress stream of the molten metal towardthe nip to eliminate belated formation of the solidified shells at andadjacent to the edges of the outer circumferential surfaces of thechilled rolls.

Extension of the ends of the nozzle to the side weirs prevents the hotmolten metal from being poured directly into just above the nip atregions adjacent to the side weirs and reduces a contact area of themolten metal to the side weirs.

Advantageous Effects of Invention

A twin roll caster according to the invention exhibits excellent effectsand advantages mentioned below.

(1) The baffles suppress stream of the molten metal toward the nip andeliminate belated formation of the solidified shells at and adjacent tothe edges of the outer circumferential surfaces of the chilled rolls, sothat the strip delivered from the nip between the rolls has no reducedthickness at regions adjacent to lateral edges of the strip and thestrip can be obtained which has uniform thickness throughout the widthof the strip.

(2) Extension of the ends of the nozzle to the side weirs prevents themolten metal from being poured into just above the nip between rolls atregions adjacent to the side weirs and eliminates belated formation ofthe solidified shells at and adjacent to the edges of the outercircumferential surfaces of the chilled rolls, so that the stripdelivered from the nip between the rolls has no reduced thickness atregions adjacent to lateral edges of the strip and the strip can beobtained which has uniform thickness throughout the width of the strip.

(3) Extension of the ends of the nozzle to the side weirs reduces thecontact area of the molten metal to the side weirs, which suppressesformation of undesired solidified shell.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing a conventional twin roll casterlooking in a direction of axes of chilled rolls;

FIG. 2 is a partial perspective view showing a first embodiment of thetwin roll caster according to the invention;

FIG. 3 is a schematic view showing the twin roll caster of FIG. 2looking radially of the chilled roll;

FIG. 4 is a partial perspective view showing a second embodiment of thetwin roll caster according to the invention; and

FIG. 5 is a schematic view showing the twin roll caster of FIG. 4looking radially of the chilled rolls.

REFERENCE SIGNS LIST

-   -   1 chilled roll    -   2 side weir    -   4 molten-metal delivery nozzle    -   8 casting pool    -   11 baffle    -   12 void    -   13 baffle    -   G nip    -   S stream

DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described in conjunction with thedrawings.

FIGS. 2 and 3 show a first embodiment of a twin roll caster according tothe invention in which parts similar to those in FIG. 1 are representedby the same reference numerals.

In a twin roll caster with chilled rolls 1, side weirs 2 and amolten-metal delivery nozzle 4, baffles 11 are provided which arecontiguous with bottoms of end faces of the delivery nozzle 4 and areprojected in a casting pool 8 toward the side weirs 2.

Tip ends of the baffles 11 may abut on the side weirs 2 or may be spacedapart from the side weirs 2 by minimum gaps, the baffles 11 being alsospaced apart from the outer circumferential surfaces of the chilledrolls 1 by minimum gaps.

In the twin roll caster, the baffles 11 suppress stream S of the moltenmetal just adjacent to the side weirs 2 directly into the nip G betweenthe rolls and guide the same in less resistive directions, i.e., towardlongitudinally intermediate portions of the chilled rolls 1, so that thehot molten metal just after the pouring does not reach the nip G alongthe side weirs 2; the molten metal considerably lowered in temperaturewith lapse of time after the pouring is guided into the nip G betweenthe rolls 1 with the rotation of the rolls.

Thus, eliminated is the belated formation of the solidified shells atand adjacent to the edges of the outer circumferential surfaces of thechilled rolls adjacent to the side weirs 2; as a result, the strip 3delivered from the nip G between the rolls has no reduced thickness atregions adjacent to lateral edges of the strip and the strip 3 can beobtained which has uniform thickness throughout the width of the strip.

The baffle 11 may be contiguous with the side weirs 2 to be projected inthe casting pool 8 toward the bottoms of the end faces of the deliverynozzle 4. When the baffle 11 is grooved at its top into gutter shape asshown in two-dotted chain line in FIG. 2, it may be expected that thestream S of the molten metal in the groove is redirected upward.

FIGS. 4 and 5 show a second embodiment of a twin roll caster accordingto the invention in which parts similar to those in FIG. 1 arerepresented by the same reference numerals.

In a twin roll caster with chilled rolls 1, side weirs 2 and amolten-metal delivery nozzle 4, ends of the delivery nozzle 4 extend toside weirs 2, respectively, guttered baffles 13 being projected fromintermediate portions on a bottom of the nozzle 4 toward the side weirs2 to form voids 12 between the baffles and the bottom of the nozzle,respectively.

Tip ends of the baffles 13 may abut on the side weirs 2 or may be spacedapart from the side weirs 2 by minimum gaps, the baffles 13 being alsospaced apart from the outer circumferential surfaces of the chilledrolls 1 by minimum gaps.

In the twin roll caster, the ends of the nozzle 4 extend to the sideweirs 2, which prevents the molten metal from being directly poured intojust above the nip G just adjacent to the side weirs. It reduces thecontact area of the molten metal to the side weirs 2, which can suppressformation of undesired solidified shell.

The steam S of the molten metal from the voids 12 adjacent to the sideweirs 2 to outside is prevented by the baffle 13 from being directlydirected to the nip G between the rolls, and is guided in less resistivedirections, i.e., toward longitudinally intermediate portions of thechilled rolls 1, so that the molten metal lowered in temperature withlapse of time after the pouring is guided into the nip G between therolls with the rotation of the rolls 1.

The steam S of the molten metal introduced into the gutter on thebaffles 13 is partly redirected upward.

Thus, eliminated is the belated formation of the solidified shells atand adjacent to the edges of the outer circumferential surfaces of thechilled rolls 1 adjacent to the side weirs 2; as a result, the strip 3delivered from the nip G between the rolls has no reduced thickness atregions adjacent to lateral edges of the strip and the strip 3 can beobtained which has uniform thickness throughout the width of the strip.

Alternatively, the baffles 13 contiguous with the side weirs 2 may beprojected in the casting pool 8 toward the bottom end faces of themolten-metal delivery nozzle 4; the tops of the baffles 13 may notalways be grooved.

It is to be understood that a twin roll caster according to theinvention is not limited to the above embodiments and that variouschanges and modifications may be made without departing from the scopeof the invention.

INDUSTRIAL APPLICABILITY

A twin roll caster according to the invention is applicable forproduction of steel and other various strips.

1. A twin roll caster comprising: a pair of parallel chilled castingrolls forming a nip between them; a molten metal delivery nozzle todeliver molten metal into the nip so as to form a casting pool of moltenmetal supported on the casting rolls above the nip; a pair of poolconfining side weirs at ends of the casting rolls, voids being locatedbetween bottoms of end faces of the delivery nozzle and the side weirs;and baffles located in the voids to suppress flow of molten metal in thecasting pool downwardly through the voids closely adjacent the sideweirs directly into the nip between the casting rolls, the baffles beinggutter shaped.
 2. The twin roll caster as claimed in claim 1, whereinthe baffles are projected from bottoms of end faces of the nozzle in acasting pool toward the side weirs, respectively.
 3. The twin rollcaster as claimed in claim 1, wherein the baffles are projected from theside weirs in a casting pool toward bottoms of end faces of the nozzle,respectively.
 4. The twin roll caster as claimed in claim 1, whereinends of the nozzle extend to the side weirs, respectively, the bafflesbeing projected from a central portion on a bottom of the nozzle towardsaid side weirs to form voids between the baffles and the bottom of thenozzle, respectively.
 5. The twin roll caster as claimed in claim 1,wherein ends of the nozzle extend to the side weirs, respectively, thebaffles being projected from said side weirs toward a central portion ona bottom of the nozzle, respectively, to form voids between the bafflesand the bottom of the nozzle, respectively.
 6. The twin roll caster asclaimed in claim 1, wherein the baffles abut on the side weirs,respectively.
 7. The twin roll caster as claimed in claim 2, wherein thebaffles abut on the side weirs, respectively.
 8. The twin roll caster asclaimed in claim 4, wherein the baffles abut on the side weirs,respectively.
 9. The twin roll caster as claimed in claim 1, wherein thebaffles abut on the nozzle.
 10. The twin roll caster as claimed in claim3, wherein the baffles abut on the nozzle.
 11. The twin roll caster asclaimed in claim 5, wherein the baffles abut on the nozzle.
 12. The twinroll caster as claimed in claim 1, wherein the molten metal deliverynozzle has an elongated nozzle trough for receiving molten metal withside walls formed with openings in lower parts of the side walls forgenerally horizontal outflow of molten metal from the trough towardouter circumferential surfaces of the casting rolls.
 13. The twin rollcaster as claimed in claim 1, wherein each baffle has a groove runningdown the baffle toward the side weir.
 14. The twin roll caster asclaimed in claim 1, wherein the baffles with a gutter shape redirectupward molten metal poured down onto the baffles.